The invention disclosed herein relates generally to mounting arrangements for panel mounted apparatus, and more particularly an easily demountable quick mounting system for panel mounted switches, indicators and similar devices.
Panel mounted electrical switches, indicators, and similar devices have long been a part of many types of industrial equipment. A considerable number of designs, techniques and arrangements have been devised accomplishing the mounting function. However, the evolution of industrial equipment has led to the use of switches and indicators in increasingly large numbers, and has placed increasing emphasis on appearance and ease of installation and removal.
For appearance the mounting should be usable with a variety of device trim configurations, including square low profile caps and trim elements. For ease of installation and removal, it is desirable that any required tools be limited to simple commonly available tools useable in limited space and requiring no more than moderate force and convenient motions, and that installation or removal be accomplished primarily from the front of the panel. It is also desirable that the mounting arrangement be self-contained, i.e., that it not require the use of loose parts, such as spacers, shims, gaskets, screws or other fasteners which are easily separated from the principal parts of the device. Finally, the mounting arrangement should readily accommodate a range of panel thicknesses. Compensation for different panel thicknesses should be provided on the back side of the panel to provide uniform front projection. The back side projection should also be constant regardless of panel thickness.
Concurrently, it is necessary to retain the features of durability and secure mounting. The mounting must be secure for both linear and rotary motions to accommodate switches having either type of operator. The durability and secure mounting requirement dictates at least a "semi-hard" mount.
A common conventional form of mounting arrangement comprises a threaded barrel which extends through an opening in the panel. A nut is mated with the barrel and tightened against the front surface of the panel. Such an arrangement is well adapted to provide a secure hard mount. However, it generally does not result in a uniform front projection with panels of different thicknesses unless a second nut or appropriate spacers are selected and placed on the barrel behind the panel. Further, such an arrangement is typically used with a circular knob, button or lens as shown in U.S. Pat. No. 2,734,953.
U.S. Pat. No. 3,264,527 issued to J. Fitzsimmons on Aug. 2, 1966 discloses a "semi-hard" switch mounting arrangement for square or rectangular switch housings. The mounting arrangement comprises a series of ridges and intervening valleys on at least one side of a rear portion of the switch housing. The ridges cooperate with a square or rectangular mounting sleeve having inwardly inclined tabs which engage the ridges as the sleeve is slipped over the switch housing. The sleeve is equipped with springs which bear on the back of the mounting panel so as to provide a firm mount even in a panel whose thickness corresponds to a tab location between valleys. Removal requires lifting of the tabs out of the valleys. Such an arrangement adequately accommodates panels of different thicknesses and installation is done predominantly from the front of the panel. However, such an arrangement has the disadvantage of requiring removal to be done from the back of the panel where the tabs on the mounting sleeve are accessible. In addition, such a device design generally requires a square or rectangular hole in the panel which, for various reasons, is less desirable than a round hole.
U.S. Pat. No. 3,446,467 issued to J. Bailey, et al., on May 27, 1969 discloses a mounting arrangement in which a switch body is configured with serrated side portions over which are fitted mounting clips having mating serrations which permit the clips to be installed in several discrete fore-aft positions to accommodate panels of different thicknesses. The clips are formed with outwardly inclined tabs for engaging the back of a mounting panel. Installation is done from the front of the panel by pushing the switch body-clip assembly through a mounting hole which depresses the tabs on the clips until they pass through the hole, at which time they spring outwardly to lock the switch in place. Such an arrangement generally does not provide a particularly secure mount and removal can only be accomplished from the rear of the panel. In addition, this configuration is primarily adapted to square or rectangular mounting holes.
U.S. Pat. No. 3,770,925 issued to T. Nelson, et al., on Nov. 6, 1973 discloses a switch mounting arrangement in which a front housing contains captive fasteners having cams which engage depressions in a barrel portion of the switch body which extends through the panel. In this arrangement, installation and removal can be accomplished from the front of the panel. However, appropriate bushings or gaskets, determined by mounting panel thickness, must be selected and placed over the barrel portion of the body during installation.
The applicant's mounting system design avoids or minimizes the previously noted shortcomings of prior mounting arrangements by utilizing captive threaded fastener means which mate with special thread engagement means capable of permitting insertion with simple linear force, but requiring rotation of the threaded fasteners for removal. Semi-hard mounting and automatic compensation for panel thickness is achieved. Installation and removal are both simply accomplished from the front of the panel without the use of special tools.